http://ucrtoday.ucr.edu/27357
[image and links in on-line article]
Novel Pretreatment Could Cut Biofuel Costs by 30 Percent or More
UC Riverside researchers have developed a novel technology that cuts the
amount of enzymes needed to produce biofuels by 90 percent or more
By Sean Nealon on February 23, 2015
RIVERSIDE, Calif. (www.ucr.edu) — Researchers at the University of
California, Riverside have invented a novel pretreatment technology that
could cut the cost of biofuels production by about 30 percent or more by
dramatically reducing the amount of enzymes needed to breakdown the raw
materials that form biofuels.
As partners in the BioEnergy Science Center (BESC), the team from the
Bourns College of Engineering Department of Chemical and Environmental
Engineering and Center for Environmental Research and Technology
(CE-CERT) have shown that this new operation called Co-solvent Enhanced
Lignocellulosic Fractionation (CELF) could eliminate about 90 percent of
the enzymes needed for biological conversion of lignocellulosic biomass
to fuels compared to prior practice. This development could mean
reducing enzyme costs from about $1 per gallon of ethanol to about 10
cents or less.
The BioEnergy Science Center is a U.S. Department of Energy Bioenergy
Research Center focused on enhancing science and technology to reduce
the cost of biomass conversion through support by the Office of
Biological and Environmental Research in the Department of Energy Office
of Science..
“As recent months have shown, petroleum prices are inherently unstable
and will likely return to high prices soon as expensive sources are
taken off line,” said Professor Charles Wyman, the Ford Motor Company
Chair in Environmental Engineering at UC Riverside. “We have created a
transformative technology that has the potential to make biofuels an
economic sustainable alternative to petroleum-based fuels.”
The findings by Wyman’s research group were outlined in a just published
paper, “Co-solvent Pretreatment Reduces Costly Enzyme Requirements for
High Sugar and Ethanol Yields from Lignocellulosic Biomass,” in the
journal ChemSusChem. Co-authors with Wyman are: Thanh Yen Nguyen,
Charles M. Cai, and Rajeev Kumar, all of whom are students or research
engineers in Wyman’s lab.
Research by the Wyman team focuses on turning agricultural and forestry
residues and other non-edible plant matter, known as lignocellulosic
biomass, into liquid transportation fuels. Lignocellulosic biomass is
attractive because it is sustainable and abundant and inexpensive
compared to oil. For example, lignocellulosic biomass costing about $60
a dry ton is equivalent in unit energy costs to oil at about $20 barrel.
(Oil is currently selling for about $55 a barrel but has hovered around
the $100 per barrel mark in recent years.) The challenge is to lower the
cost of processing low cost biomass sources into fuels.
Lignocellulosic biomass is composed of hemicellulose, cellulose, and
lignin, and biological processes favored for making liquid biofuels
convert the hemicellulose and cellulose into sugars that can in turn be
fermented into biofuels. However, the complex structure of
lignocellulosic biomass makes it difficult for enzymes to release these
sugars, and a pretreatment step using heat and chemicals is needed to
reduce this recalcitrance enough to realize the high yields vital to
economic success. The lignin left in biomass after most pretreatments
presents a particular problem by impeding enzyme access to hemicellulose
and cellulose, thereby hurting product yields and requiring more enzyme
at a substantial cost.
CELF, the pretreatment developed at UC Riverside, solves those problems.
In the ChemSusChem paper, the UC Riverside researchers outline
laboratory results in which they compared the total achievable combined
sugar yields between CELF pretreatment and dilute acid pretreatment, a
current leading strategy, coupled with subsequent enzymatic hydrolysis
in three timeframes with three levels of enzymes.
Using the dilute acid method, the sugar yield was only about 70 percent
of the maximum possible after 14 days when two milligrams of enzymes
were used. That percentage increased to about 85 percent in 14 days when
15 milligrams of enzymes were added.
By contrast, CELF pretreatment increased sugar yields to about 95
percent of the maximum possible regardless of whether two milligrams,
five milligrams, or 15 milligrams of enzymes were added. Furthermore,
the time required to reach these high yields dropped to five days when
five milligrams of enzyme were used and two days when 15 milligrams of
enzyme were used.
In addition to such drastic cutting of the amount and cost of enzymes
needed to realize nearly theoretical sugar yields, CELF is capable of
dissolving and extracting up to 90 percent of the lignin in corn stover
and even more for woody biomass. After pretreatment and enzymes release
of the sugars from hemicellulose and cellulose, previous process
strategies have focused on burning the residual lignin, which is a low
value proposition. However, lignin has promise as a resource from which
to make additional high value chemicals and fuels once it is extracted
and depolymerized with CELF.
“These findings are very significant because they establish a new
pretreatment process that can dramatically reduce enzyme loadings and
costs, thereby improving the competitiveness for biological conversion
of lignocellulosic biomass to fuels,” said Wyman, who has focused on
understanding and advancing biofuels technologies for more than 30
years. “Understanding the mechanisms responsible for achieving these
intriguing results can also suggest even more powerful paths to
improving the economics of converting non-edible biomass into
sustainable fuels.”
The National Science Foundation contributed to making this project
possible through their Graduate Research Fellowship Program. Initial
application of CELF to biological conversion was supported by the UC
Riverside Research and Economic Development Office of Technology
Commercialization and the University of California Transportation Center.
The UC Riverside Office of Technology Commercialization has worked with
the inventors to file a patent on the invention. CELF is now exclusively
licensed by partners from CogniTek in Northbrook, Ill., who will be
working with Cai and Wyman to launch a new spin-off company, MG Fuels,
to commercialize the technology.
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